Fretting fatigue Behaviour of Inconel 718 at room and high Temperature

This thesis analyses the fatigue behaviour of Inconel 718, a Nickel-Chromium-based superalloy known for its excellent mechanical properties and high resistance to corrosion and oxidation, even at elevated temperatures. The study combines experimental testing and numerical simulations in order to accurately characterise the material's response to fretting damage. To this end, a cylindrical contact configuration was used, consisting of a rectangular cross-section "dog-bone" specimen pressed against a cylindrical pad. The setup was assembled using a device commonly referred to as a “fretting bridge.” Both plain fatigue and fretting fatigue tests were carried out under different levels of axial and normal load, and at two different temperatures: room temperature and 650?°C. Additionally, interrupted tests were performed to monitor damage progression, and friction coefficients were measured under various conditions. The experimental results were thoroughly analysed, identifying the influence of temperature and applied loads on the fatigue life of the material. A fractographic analysis of the tested specimens was subsequently conducted using scanning electron microscopy (SEM), which enabled the identification of distinct regions on the fracture surface, as well as the establishment of correlations between the type of damage observed and the test conditions. Furthermore, crack growth rates under different conditions were estimated and compared with data available in the literature. To complement the experimental work, a numerical model was developed using the finite element method, aimed at simulating the stress and strain fields generated in the contact area. This model allowed the influence of loading and temperature conditions on the material’s behaviour to be assessed. Finally, a fretting fatigue life prediction model was applied, which simultaneously considers both the crack initiation and propagation phases, without the need to define a transition point between them. The predicted results were compared to experimental data, showing good correlation and validating the model’s usefulness for fatigue life estimation in components subjected to fretting conditions. Overall, the work presented provides a comprehensive characterisation of Inconel 718’s behaviour under fretting fatigue, offering valuable insights for the design of critical components operating under severe service conditions.

Author dc:creator

• Moreno Rubio, María

Advisors dc:contributor.advisor

• Navarro Pintado, Carlos
• Vázquez Valeo, Jesús

Statement dc:rights

• Attribution-NonCommercial-NoDerivatives 4.0 International

Licence dc:rights.uri

• http://creativecommons.org/licenses/by-nc-nd/4.0/

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/11441/177915

OAI identifier oai:identifier

oai:idus.us.es:11441/177915